1. Field of the Invention
The present invention generally relates to the technical field of prepayment using communication terminals.
2. Description of the Related Art
In this technical field, in order to improve security of business transactions and user-friendliness, it is widely adopted to make payments in advance by using prepaid cards. For example, prepaid card companies issue prepaid cards that are specified to be equivalent to 500 Yen, 1000 Yen, 3000 Yen, respectively, and users purchase these prepaid cards of a desired amount of money. The prepaid cards, for example, are made to be exclusively used to pay for phone calls. In order to pay for phone charges using a prepaid card, a user accesses a prepaid card management system first, and following the guidance, for example, the user operates keys on the keyboard of a cellular phone to input the card number printed on the prepaid card, and to connect to the management system. Receiving the connection request from the user, the management system first authenticates the prepaid card. Then depending on the type of the prepaid card, the management system appropriately calculates the phone charges of a relevant communication terminal, for example, a cellular phone, or a wire line telephone.
Such a prepaid system has been disclosed, for example, in Japanese Unexamined Patent Publication No. 2001-325541. Such a system is not limited to payment of phone charges, but also applicable to normal electronic business transactions.
To utilize the prepaid system of the related art, however, users have to go to special shops to buy the tangible prepaid cards, and this is not convenient to the users. Further, this also imposes a great load on card companies and management systems. In addition, when using the prepaid cards, users have to operate keys one by one to input card numbers, each of which usually has more than 10 digits, and this is often quite cumbersome. Moreover, if input errors occur, the management system has to cope with them, and this increases the burden of the management system. As described here, a prepaid system of the related art is not able to really lighten work loads of users and the system managers.
In addition, in the prepaid system of the related art, the total amount of money in a prepaid card is charged once, so a prepaid card can be used only once. In other words, the money in a prepaid card cannot be partially used, hence cannot be used for several times to make several payments. For example, when paying for telephone charges with a 1000 Yen prepaid card, the 1000 Yen is charged once. As a result, prepaid cards having a larger amount of money are inconvenient compared with prepaid cards having a smaller amount of money. Further, a user of a telephone can only pay for telephone rate of the user himself, that is, when keys of a telephone are operated to input card numbers following the voice guidance, telephone charges of that very telephone are paid. So, payments made from other telephone sets are not allowed. Therefore, even though such prepaid cards are presented to a person, without complicated operation this person cannot use the cards to pay for phone charges for himself. Due to the above reasons, the prepaid cards each having a large amount of money (below, abbreviated as “high-amount prepaid card”) are seldom used, while those cards each having a small amount of money (below, abbreviated as “low-amount prepaid card”) are relatively prevalent.
Nevertheless, it is quite bothersome for users to buy appropriate prepaid cards according to the actual charges each time, and it is not desirable either for the card company to issue a large number of low-amount prepaid cards. Therefore, the burdens of both the users and the management system are not reduced presently.